Acute respiratory infections (ARI) are among the most common reasons for seeking medical attention in the United States. Rhinovirus, influenza, and increasingly respiratory syncytial virus (RSV) are recognized as leading etiologies of ARI in adults. Upper respiratory tract infections caused by most viruses are generally self-limited, although among individuals with pre-existing pulmonary disease, viral infection can lead to disease exacerbation. Most adults experience at least one rhinoviral infection per year. While most rhinoviral infections are self-limited, these infections are also important causes of exacerbations of chronic obstructive pulmonary disease and asthma. Adult RSV infections may be self-limited or lead to significant airways obstruction and morbidity. Influenza infection remains common among community-living persons, with associated significant health-care and societal costs. Furthermore, new strains of influenza, such as H1N1, pose the risk of pandemic infection. Thus, early detection of influenza A can facilitate individual treatment decisions, as well as provide early data to forecast an epidemic/pandemic.
Discrimination between infectious causes of illness is a critical component of acute care of the medical patient as such distinctions facilitate both triage and treatment decisions. While traditional culture, antigen-based, and PCR based diagnostics are useful in classifying infectious pathogens, these assays are not without limitations. See, e.g., Bryant et al., “Chips with everything: DNA microarrays in infectious diseases,” Lancet Infect Dis (2004) vol. 4, 100-111; Campbell and Ghazal, “Molecular signatures for diagnosis of infection: application of microarray technology,” J Appl Microbiol (2004) vol. 96, 18-23, both of which are incorporated by reference in their entireties. As reported, current rapid diagnostic methods lack sensitivity. See, e.g., Jonathan, “Diagnostic utility of BINAX NOW RSV—an evaluation of the diagnostic performance of BINAX NOW RSV in comparison with cell culture and direct immunofluorescence,” Ann Clin Microbiol Antimicrob (2006) vol. 5, 13, evaluating influenza and RSV tests of Inverness Medical Innovations (Waltham, Mass.), incorporated herein by reference in its entirety. Jonathon reports sensitivities of only 53-80%. Other know tests, such as direct-fluorescent antibody (DFA) testing, are labor-intensive and slow.